Chapter 3

Pre-hospital Rapid Sequence

Intubation (PRSI)

By the end of this chapter you will be able to:

• List the six P’s of PRSI• Discuss each of the P’s in turn• Appreciate the importance of a plan B

3.1 The Six P’s (Fig. 3.1)

PRSI can be separated into six phases:1. Preoxygenation2. Preparation3. Premedication4. Paralysis and Sedation5. Passage of the Endotracheal tube6. Post intubation care It is important that each member of the team is familiarwith all phases of PRSI. This allows preparation to take placeconcurrently with ongoing patient management.

Figure 3.1 The 6 P’s

3.2 PreoxygenationThis is an essential phase in the conduct of safe PRSI. It providesan oxygen safety buffer to prevent precipitous desaturationoccurring in the period of hypoventilation and apnoea, prior toand during laryngoscopy. Desaturation below an oxygen satu-ration (SpO2) of 70 %, places patients at risk of cardiovascularinstability, hypoxic organ damage and death (Mort 2004). 3.2 Preoxygenation 37

Desaturation is a significant complication of PRSI. The

Scottish Emergency Medical Retrieval Service found that15.4 % (32 of 208 patients) had a desaturation episode dur-ing the procedure (below 90 % or a reduction in >10 % frominitial SpO2) (Wimalasena et al. 2014). The aim of preoxygenation is to replace the air in thealveoli with an enriched oxygen mixture, particularly in thefunctional residual capacity of the lungs. This will act as areservoir for the body during apnoea. In ideal conditions thisoffers several minutes before desaturation occurs (Fig. 3.2,Box 3.1). Unfortunately, conditions for PRSI are rarely ideal,and critically ill patients with increased metabolic demand,hypovolaemia, reduced cardiac output and possible lunginjury will desaturate far quicker than this.

Box 3.1: Approximate Time for Desaturation to 90 %

3.2.1 Preoxygenation Strategies

Preoxygenation should be performed using a tight-fitting

face mask with a reservoir and ≥15 L/min of oxygen in orderto provide a high (>0.9) fraction of inspired oxygen (FiO2)during inspiration. In hospital this is done using either astandard anaesthetic circuit or a disposable Mapleson C(sometimes called a ‘Waters’ circuit) with adjustable pressurelimiting (APL) valve (Fig. 3.3). This also allows an element of

Figure 3.3 Mapleson C circuit With adjustable pressure limiting

(APL) valve being used to apply CPAP 3.2 Preoxygenation 39

continuous positive airway pressure (CPAP) to be applied, as

long as the face mask is tight-fitting. These systems requirea constant high flow of oxygen and a tight seal to allowmanual ventilation, neither of which can be guaranteed inthe pre-hospital setting. The default system in the emergencysituation is a self-inflating bag-valve-mask (BVM), of whichthere are many varieties, including many single-use versions.Some older versions of BVMs did not have one-way exhala-tion valves near the mask and therefore allowed entrainmentof air into the face mask at lower oxygen flow rates. Thesewould deliver relatively low FiO2 (<0.4) during spontaneousventilation (Mills et al. 1991; Nimmagadda et al. 2000). Thisis not the case with the majority of BVM systems currentlyin use, however, it is always important to check the type ofBVM being used. Even when a BVM has a one-way exhalation valve, thereis variation in the FiO2 delivered by different BVM systemsin common use. As an example, two single-use BVMs withexactly 15 L/min of oxygen attached, were compared for bothease of breathing and delivered FiO2 (using a calibrated oxy-gen analyser in a t-piece behind the face mask). The Ambu Single Patient Use Resuscitator (SPUR)II (Fig. 3.4a) has an extremely low resistance inspiratory/expiratory single-shutter (one-way) valve at the patientend (Fig. 3.4b) which provided only minimal resistance tobreathing. The valve prevents entrainment of air duringinhalation, so only oxygen from the bag is inhaled if themask is correctly sealed on the patient’s face. Even duringlarge inspiratory breaths, the FiO2 remained above 0.9 at alltimes and at normal tidal volumes was 0.95. The large safetyinspiratory valve at the reservoir bag end of the BVM assem-bly (Fig. 3.4c) is designed to allow air to be entrained if thereservoir bag is completely empty, to prevent asphyxiation.This only opened a little even during large tidal volumes;hence the FiO2 only dropped slightly due to indrawn air mix-ing with the oxygen. The Marshall Classic Manual Resuscitator (Fig. 3.5a) has aLaerdal type ‘duck-billed’ inspiratory valve and a flat silicone40 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

ring one-way expiratory valve at the patient end (Fig. 3.5b).

The ‘duck-billed’ valve is subjectively more difficult tobreathe through. The additional negative pressure generated,along with the small size and lightweight safety inspiratoryvalve (Fig. 3.5c), means that air is entrained through the valveeven during relatively small volume breaths. This reducedthe measured FiO2 from 0.9 at normal tidal volume downto 0.75 during larger inspiratory breaths. It is useful to knowthat both the ease of breathing and the inspired FiO2 can beimproved significantly by gently squeezing the bag in timewith the patient’s inspiration. Even more important than the design of the valves is agood seal between the mask and the patient’s face. Gas willalways take the path of least resistance. During inspirationwith a poor seal, gas will be entrained around the edges of 3.2 Preoxygenation 41

b c

Figure 3.5 (a) Marshall Classic Resuscitator, (b) ‘Duck-billed’

inspiratory valve. (c) Inspiratory safety valve

the mask rather than drawing from the oxygen in the bag andreservoir via the one-way inspiratory valve. The requirementfor a good face seal also applies to disposable non-rebreathereservoir masks; the path of least resistance is also aroundthe edge of the mask rather than through the one-way valve(although the resistance through the valve does tend to beless than in a BVM). With a good seal and a patient with reasonable inspiratoryeffort, a BVM with a reservoir bag and >15 L/min will pro-vide a high FiO2 (>0.9) and avoids the requirement to changeface mask during the RSI (Nimmagadda et al. 2000). It alsomeans that ventilation can be easily assisted if inspiratorybreaths are shallow or if SpO2 drops whilst waiting for themuscle relaxant to work. BVM preoxygenation does, however, require a competentadditional person to maintain the tight face seal whilst the42 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

team is preparing for RSI. It may be more practical (and also

possibly less daunting for the patient), to use a well-fitting‘non-rebreathe’ face mask with reservoir bag for preoxygen-ation. This is held in place with an elastic strap placed behindthe head. Basic models are not ideal as they have a thinplastic edge that may not create a good seal, and an openhole in one side of the mask that allows air to be entrainedif the oxygen supply fails (Fig. 3.6). Both of these factorscan result in a relatively low FiO2 (0.6–0.7), even at veryhigh oxygen flow rates. Newer rebreathe masks have softercushioned edges, which improve the seal, and have no open

Figure 3.6 Basic non-rebreathe mask

3.2 Preoxygenation 43

holes in the sides of the mask, thereby increasing the chance

of delivering an FiO2 closer to 0.9 whilst freeing up an extraperson (Fig. 3.7). With additional nasal cannula oxygen, asdescribed below, this can increase the FiO2 further (Fig. 3.8).Clearly if the patient requires assistance to maintain airwaypatency or needs assisted ventilation, this benefit of freeinga person is lost. Three minutes of normal tidal volume breaths is accept-able preoxygenation for most patients. This preoxygenationcan be improved by asking the patient to fully exhale and

Figure 3.7 Newer non-rebreathe mask

44 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

Figure 3.8 Non-rebreathe oxygen mask with additional nasal can-

nula in place for apnoeic oxygenation during PRSI

inhale (vital capacity breaths), although most patients in

the pre-hospital setting are unable to co-operate with sucha request. Analgesia prior to preoxygenation may improvethe effectiveness by reducing pain from chest trauma andincreasing inspiratory volumes. In agitated patients it may be necessary to use sedationto facilitate preoxygenation. Small doses of Midazolam(1–2 mg) or Ketamine (10–40 mg) should be titrated toeffect. Weingart et al (2015) reported the successful use ofKetamine 1 mg/kg (+/− further 0.5 mg/kg aliquots) to facili-tate preoxygenation in agitated patients. This then allowed3 min of pre-oxygenation, before full sedation and a musclerelaxant were given. Although based on a relatively smallconvenience sample of patients unable to tolerate preoxy-genation due to delirium, they demonstrated the ability toincrease mean pre-laryngoscopy SpO2 from 89.9 to 98.8 %,and reported no complications such as pre-muscle relaxantapnoea, peri-intubation emesis, cardiac arrest or death, from 3.2 Preoxygenation 45

doing so. Preoxygenation was achieved with a high flow

non-rebreathe oxygen mask, or non-invasive CPAP if SpO2<95 %. They commented that facilitating preoxygenation inthis manner avoids the risks of proceeding to RSI withoutan adequate oxygen reserve in the patient, and the poten-tial risks of peri-intubation BVM ventilation that may berequired to prevent desaturation; such as gastric insufflationand aspiration. They termed this ‘delayed sequence intu-bation’ although it is essentially just sedation to facilitatepreoxygenation. This concept has been advocated on thePHA course for several years. SpO2 will fall precipitously during the 45–60 s of apnoeawhilst awaiting onset of muscle relaxation, if starting SpO2is already low. In these patients, if already receiving oxygenthrough a BVM, it may be advisable to gently augment thepatient’s own respiratory effort prior to induction in order tomaintain a safe oxygen saturation throughout the procedure.CPAP can also be applied to improve oxygenation if it ispossible to fit an external positive end expiratory pressure(PEEP) valve to the BVM. If ventilation is continued following induction and apnoea,cricoid pressure will help to avoid the associated gastricinsufflation and reduce the risk of aspiration, although thismay make ventilation more difficult in some cases. BVMventilations should aim to be delivered slowly with both lowvolume (6–7 mL/kg) and low rate, in order to avoid inspira-tory pressures sufficient to overcome the lower oesophagealsphincter pressure. There is evidence that head-up positioning delays the timeto desaturation during apnoea (Lane et al. 2005; Ramkumaret al. 2011). It may also reduce the risk of passive regurgita-tion. This may be achieved by using a semi-recumbent posi-tion on a stretcher trolley or, in trauma patients requiringspinal immobilisation, a reverse-trendelenburg position, withthe head of the spinal board/scoop stretcher/trolley raised 30°above the feet.46 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

3.2.2 Apnoeic Oxygenation

Although described in the medical literature for over a

century, the application of apnoeic oxygenation to pre-hospital airway management procedures is relatively recent(Weingart et al. 2011). It utilises the physiological principlethat even without respiratory effort, approximately 250 mL/min oxygen is taken from the alveoli into the bloodstream.If oxygen is supplied to a patent upper airway, a mass flowof gas from the pharynx to alveoli maintains this diffusion ofoxygen into the bloodstream, and in doing so, maintains oxy-genation without ventilation. The Greater Sydney HelicopterEmergency Medical Service (HEMS) has included apnoeicoxygenation in their PRSI standard operating procedure(SOP) since 2011. During the preoxygenation phase, whilsta non-rebreather mask or BVM set at 15 L/min oxygen isused to preoxygenate, nasal cannulae are applied and setto 5 L/min oxygen, as tolerated (Fig. 3.8). After inductiondrugs are administered, the flow rate of the nasal cannulae isincreased to 15 L/min until the endotracheal tube is secured(Wimalasena et al. 2015). During the 22-month period priorto apnoeic oxygenation, 22.6 % of patients had a desatura-tion episode below 93 % during RSI, compared to 16.5 % ofpatients in the 22-month period after introduction of apnoeicoxygenation to the SOP. They suggest this simple and inex-pensive technique is of clear clinical benefit to critically illand injured patients undergoing PRSI.

3.3 PreparationPerformance of a rapid sequence intubation is not immediateand requires time for preparation. The time spent in the prep-aration phase is never wasted and will increase the chancesof a swift and safe intubation. There are four elements topreparation for PRSI (Box 3.2). 3.3 Preparation 47

Box 3.2: Preparation

Preassessment should be easily remembered with a familiar

<C>ABCDE approach. It is a similar, but much more rapidassessment, to that which occurs before any anaesthetic in thehospital environment.

3.3.1.1 Catastrophic Haemorrhage

Catastrophic haemorrhage should be controlled at the earli-

est opportunity during pre-hospital management. This mayinvolve use of wound packing and direct pressure, haemo-static agents and tourniquets. Reducing blood loss and pro-moting clotting at this earliest stage, not only is beneficial tothe patient overall, but also promotes haemodynamic opti-misation in preparation for PRSI. Splinting fractures of thepelvis and long bones (particularly femur) is important andwill also minimise blood loss, but this occurs after assessmentof the Circulation (Sect. 3.3.1.4).

3.3.1.2 Airway

The main concerns are to achieve maximum airway patency

to allow preoxygenation prior to RSI, and to be able to pre-dict the likelihood of a “difficult airway.”48 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

Difficult AirwayThe definition of a difficult airway is that a trained clinicianexperiences difficulties with mask ventilation, endotrachealintubation or both (American Society of Anesthesiologists(ASA) 2013). Difficult mask ventilation is defined as a situationwhen it is impossible to maintain SpO2 above 90 % or it is notpossible to reverse signs of inadequate ventilation with a BVMand 100 % oxygen. The incidence of difficulty in airway mainte-nance in trauma patients can be up to 18 % (Smith and Dejoy2001). The incidence of a difficult airway is likely to be higherin the pre-hospital environment, for reasons mentioned earlier.Airway assessment should therefore include a judgment of thelikely ease of airway maintenance with a BVM, as well as thepotential for difficult intubation. The anticipation of difficultymay require a change of the initial management plan (Box 3.3).

Box 3.3: Reasons for Difficulty in Maintaining an Airway

Difficult IntubationDifficult intubation is defined in many different ways in vari-ous studies, making comparative reporting difficult. The 2013guidelines of the ASA divide difficult intubation into two parts:difficult laryngoscopy and difficult intubation. Difficult laryn-goscopy is defined as being unable to visualise any portionof the vocal cords after multiple attempts at conventionallaryngoscopy (i.e. Cormack-Lehane grade ≥3 (Fig. 3.20)), anddifficult tracheal intubation as the requirement for multipleattempts. (This was previously described by the same groupas more than 3 attempts or requiring more than 10 min withconventional laryngoscopy (ASA 1993)). Failed intubation isthen described as failure to place the endotracheal tube after 3.3 Preparation 49

Class 1 Class 2 Class 3 Class 4

Figure 3.9 Airway assessment – modified Mallampati classification.

The view of the pharyngeal structures is observed, with the mouthopen and tongue protruded maximally (Reproduced by kind per-mission Anaesthesia UK Website)

‘quick look’ assessment generated sensitivity of 0.597 and

specificity of 0.763, with positive predictive value of 0.336 andnegative predictive value of 0.904, demonstrating some utilityof this method, although not in isolation. The Modified Mallampati classification of airway assess-ment (Fig. 3.9) is a commonly used tool in the hospitalenvironment to predict difficult intubation (likelihood ofdifficulty increases from Class 1 to Class 4). Unfortunatelyit requires an awake and cooperative patient, so it is usuallynot useful in patients requiring pre-hospital RSI. Other pre-dictors of difficult intubation may be present (Box 3.4). The‘LEMON’ assessment tool, is one system commonly taughtfor emergency airway assessment which combines most ofthese factors into a mnemonic (Box 3.5).

Clinical Signs of Potential Difficult Intubation or Ventilation

Obese PatientsObese patients or those with short muscular necks can bedifficult to intubate and ventilate. Excess soft tissue aroundthe airway may hinder displacement during laryngoscopy.This may affect the view. These tissues may also collapse 3.3 Preparation 51

over laryngeal structures making manual ventilation difficult.

Two-handed mask ventilation with an oropharyngeal airwaymay be required.

Edentulous PatientsEdentulous patients are often easy to intubate but can bedifficult to manually ventilate. The lack of teeth leaves lesssupport for the cheeks, and as a result the face mask seal maybe poor. This can be remedied with a two-handed technique52 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

bunching the facial tissue up into the mask to achieve a seal.

Again an oropharyngeal airway may make ventilation easier.Early intubation or use of a laryngeal mask airway (LMA)may be required if ventilation is inadequate.

“Chinless” PatientsPatients with micrognathia (receding chin) usually have ananterior larynx. There is a reduced thyromental distance: tipof chin to thyroid cartilage (Adam’s apple) of <6.5 cm withthe neck extended. This measurement is therefore not practi-cal when cervical spine injury is a concern. An impressionof micrognathia should still be a visual clue. These patientsdo not have enough space to displace tissue forward toallow intubation. Laryngeal manipulation such as backwardupward rightward pressure (BURP) and a bougie will oftenbe required. (Note: Male patients often grow a beard to hidea small chin).

“No-Neck” PatientsA reduced sternomental distance (tip of chin to sternum<12.5 cm) is predictive of a difficult intubation. Again, thismeasurement is based on the head in an extended positionand is therefore not usually practical. Subjective appearancemay add to your assessment of difficulty.

Bearded PatientsAs well as sometimes hiding micrognathia, a beard makes itdifficult to achieve an adequate seal with a face mask to allowventilation. Applying lubricating jelly to the beard and usinga two-person technique will improve the situation. An LMAmay be required to ventilate if intubation is not possible.

“Goofy” PatientsA prominent overbite (protruding upper teeth) can impedelaryngoscopy. It may be difficult to manoeuvre the laryngo-scope without levering on the upper teeth. External pressure 3.3 Preparation 53

on the larynx (above the cricoid cartilage) i.e. BURP, and useof a Macintosh No. 3 blade, inserted fully inside the mouth(past the top teeth), may help.

“Stiff-Neck” PatientsIn patients with poor neck mobility, the larynx will, in effect,be more anterior. In patients with no risk of neck instabil-ity, elevating the head further to compensate for reducedextension of the head along with thyroid pressure and abougie, gives the best chance of success. If there is a chanceof underlying instability and risk of spinal cord injury (e.g.severe rheumatoid arthritis), no head or neck movementshould take place. The only movement that is appropriateis jaw distraction.

Bleeding (Oral) Patients

Management of patients with blood in the oropharynx canpresent a particular challenge to the intubator. These patientsare best managed in a slightly head-down position. Thisallows blood to pool in the upper pharynx away from thevocal cords. Adequate suction is the key to success; two suc-tion devices may be required.

Remember A predicted difficult intubation may actually

be easy but conversely some “easy” intubations turn out tobe difficult. This necessitates the need for a fallback plan or“Plan B” (see text later).

3.3.1.3 Breathing

The initial assessment will have determined the urgency for

PRSI. A hypoxic patient with a poor respiratory effort willprompt a more rapid response than one with adequate oxy-genation and ventilation but who has a reduced GCS. If a pneumothorax has been diagnosed, this should havebeen treated at least with needle thoracocentesis (Appendix54 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

“Needle Thoracocentesis”) prior to intubation. Positive pres-

sure ventilation can rapidly change a pneumothorax into atension pneumothorax, resulting in profound cardiovascularcollapse. A thoracostomy ± drain (Appendix “Thoracostomy &Chest Drain Insertion”) must be performed immediately afterPRSI. (Note: Thoracostomy without a drain is only permissible ina ventilated patient. If the patient is breathing spontaneously,a thoracostomy will create an open pneumothorax, whichwill not improve ventilation. A valve system to prevent airentrainment during inspiration is therefore required i.e., achest drain. (A needle/cannula thoracostomy is acceptablebefore RSI as this allows the release of a “tension” but istoo small to allow any significant entrainment of air duringinspiration)).

3.3.1.4 Circulation

Intravenous (IV) access is required and should be checked

with a 10 mL flush to ensure patency. This must be ade-quately secured (IV sites are particularly vulnerable in thepre-hospital environment.) Ideally two sites of IV access areobtained prior to RSI in major trauma. This allows rapid infu-sion of blood products/fluids in one whilst leaving anotheravailable for drugs, including those for PHA. It is, however,not always practical or possible due to limb injuries or patientagitation. In the critically ill patient intraosseous (IO) access maybe appropriate if two attempts at IV access have failed orvenous access is clearly very poor. Although originally onlyused in children, adult IO access for emergency resuscitationhas become an accepted technique over the last few years,partly due to successes reported in military use (Cooper et al.2007). IV access is still preferable, as fluids will flow moreeasily, whereas IO access requires pressurisation of fluid bagsor use of a 50 ml syringe and 3-way tap to achieve adequateflow rates for fluid resuscitation. All RSI drugs can be admin-istered via IO access, with intubation success rates (first pass 3.3 Preparation 55

intubation and grade of view) that match those of IV induc-

tion (Barnard et al. 2014). Even in the pre-hospital environment, IV or IO accessshould be gained as aseptically as possible. Wipes (2 %chlorhexidine in 70 % alcohol) should be used to clean theskin, and minimal handling of the puncture site is advocated.Where asepsis is not possible, it is worth noting this duringhandover, so the receiving hospital staff can replace it as soonas practical. Induction of anaesthesia is challenging in the haemo-dynamically unstable patient, requiring appropriate tim-ing within the resuscitation, and careful drug dosing. Theassessment of shock (inadequate tissue perfusion) in thepre-hospital patient can be difficult. Skin colour and capillaryreturn may be misleading in a cold environment. Confusionand level of consciousness may be lost as a guide to adequateperfusion if there is a coexisting head injury. Heart rate canbe very useful, but is not specific to changes in volume status.Tachycardia may result from sympathetic stimulation second-ary to inadequate analgesia (or sedation when the patient isintubated). Bradycardia may be due to beta-blockers, highspinal cord injury or be may be heralding a pre-terminalevent. In the absence of a measured blood pressure, the pres-ence, site and character of peripheral pulses may give usefulinformation about cardiovascular status (e.g. no palpableradial pulse or a weak/’thready’ pulse. It is sometimes saidthat the presence of a radial pulse implies a blood pressureof 80–90 mmHg and the presence of a carotid pulse equatesto a blood pressure of 60–70 mmHg, however, this has notbeen validated (Greaves et al. 2000). There is no doubt thatthe presence of a radial pulse implies a higher blood pressurethan the presence of a carotid pulse alone. In the majority of pre-hospital cases, hypotension will besecondary to hypovolaemia. If haemorrhage is external, com-pressible and controlled, it may be reasonable to give furtherfluid to aim towards a more normal Mean Arterial Pressure(MAP) for that patient. Conversely, if the hypovolaemia56 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

is due to internal, non-compressible haemorrhage, current

opinion is that further fluid should be withheld unless theradial pulse becomes impalpable once more (or the bloodpressure drops below 80 mmHg systolic/conscious leveldrops). The reasoning behind this is that an increase in bloodpressure may dislodge a newly formed clot, thus resultingin greater loss of blood. In addition, if fluid resuscitation isnot with blood products, dilutional coagulopathy will occur.Some UK HEMS units now carry blood products (redcells +/− plasma), and in the bleeding patient this would beused in preference to crystalloid in order to provide more‘haemostatic’ resuscitation. In the absence of blood prod-ucts, a 250 mL bolus of either a ‘balanced’ crystalloid (e.g.Hartmann’s) or 0.9 % NaCl is recommended. Crystalloidsare preferred to colloids. A Cochrane Review in 2013 con-cluded: ‘There is no evidence from randomised controlled tri-als that resuscitation with colloids reduces the risk of death,compared to resuscitation with crystalloids, in patients withtrauma, burns or following surgery. Furthermore, the use ofhydroxyethyl starch might increase mortality. As colloids arenot associated with an improvement in survival and are con-siderably more expensive than crystalloids, it is hard to seehow their continued use in clinical practice can be justified’(Perel et al. 2013). The concept of allowing the blood pressure to remain lowin order to minimise further blood loss is termed ‘permis-sive hypotension’. Prolonged hypotension will, however,increase the likelihood of both multi-organ failure due tohypoperfusion and worsening of coagulopathy due to the‘Acute Coagulopathy of Trauma’ (ACoT) (Brohi et al. 2007).ACoT appears to be due to tissue hypoperfusion. This wouldseem to support previous practice of giving aggressive fluidresuscitation to normalise the blood pressure of a traumapatient, as this should theoretically reduce ACoT. This leavesthe pre-hospital practitioner with two apparently conflictingcourses of action. The British Military currently advocates‘novel hybrid resuscitation’, whereby hypotensive resuscita-tion is practised for the first hour after injury, followed by 3.3 Preparation 57

normotensive resuscitation. The rationale for this compro-

mise is that clot will form and become sufficiently robustin that first hour, then by increasing blood pressure toallow normal perfusion, ACoT and organ failure should beminimised. In patients who have sustained a severe head injury, hypo-tensive resuscitation is not appropriate. These patients mayhave reduced Cerebral Perfusion Pressure (CPP) secondaryto a raised intra cranial pressure (ICP) and a further lower-ing of MAP would risk cerebral ischaemia. A compromise forpatients with severe head injury (GCS <8) and ongoing/non-compressible haemorrhage, is a target MAP of >80 mmHg(Spahn et al. 2013). Hypothermia (<35 °C) will also have an effect on coagu-lopathy. Ideally all fluids should be warmed and effortsmade to minimise heat loss (e.g. reflective/insulated/heat-generating blankets, heated transfer vehicle).

3.3.1.5 Disability

In head-injured patients, particular attention should be

placed on pre-sedation pupil responses and GCS, particu-larly the motor score, as these have the most prognostic sig-nificance (along with age and CT scan appearance) (Murrayet al. 2007). It should be documented and communicated onhand over. Level of consciousness may also affect the amount ofinduction agent given, however it should be remembered thatone of the reasons for giving the induction agent is to obtundthe hypertensive response to laryngoscopy. This dose may besimilar whether the patient is unconscious or not.

3.3.1.6 ExposureExposure of the patient may have occurred to varying extentsto allow a primary survey to be conducted. Maintaining nor-mothermia of the patient is the target, and it is important to58 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

keep the patient protected from the elements where possible.

The head and neck will clearly need to be exposed for intuba-tion, as will the chest when confirming position afterwards. Visualising the larynx is likely to be more difficult in thepresence of driving rain, sleet or snow, and unfortunatelyalso in bright direct sunlight. It may be appropriate tomove the casualty prior to attempting intubation in adverseweather conditions (e.g. undercover or into an ambulance).Alternatively a ground sheet or similar may be held abovethe casualty if other emergency service personnel are ableto assist. (Note: In certain situations, access to intubate thepatient may be severely restricted and in these cases it isinvariably safer to move the casualty first.) Inducing and paralysing a patient in a confined areais asking for trouble. A nasopharyngeal airway and rapidextraction is more appropriate. It is also worth noting that ina CBRN (Chemical, Biological, Radiological, Nuclear) envi-ronment most authorities advocate simple airway manoeu-vres until the casualty has been removed from the hazard anddecontaminated.

3.3.1.7 History

If possible some basic history should be sought with special

reference to anaesthesia. The AMPLE history is acceptable(Box 3.6). If the patient is conscious, their name, date of birthand next of kin details allow for more effective administra-tion in hospital.

Box 3.6: The AMPLE History

3.3.2 Prepare Equipment and Drugs

The equipment required for intubation should have a stan-

dard configuration and everyone in the team should befamiliar with it. It should be packed so that all items are easilyaccessible. Equipment bags based on the tool-roll principlecan be effective for this purpose. These open out into a pre-dictable configuration with individual items held securely inplace. Items can be easily checked and are immediately athand, and are unlikely to be left behind when withdrawingfrom the scene. Alternatively a “kit dump” can be preparedon a clean folded drape or clinical waste bag (Figs. 3.10 and3.11). This has the advantage of being easily seen and avoidedby other emergency service personnel.

3.3.2.1 PRSI Checklist (Appendix “PRSI Checklist”)

Most airway equipment is single use, and it is generally

advocated that it remains in original packaging until use. Allequipment should be checked in the pre-RSI phase. The teamdoes this together, with one calling out the list and the otherchecking the kit (Fig. 3.12). Laryngoscope handles should

Figure 3.10 The equipment required to safely conduct PRSI

60 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

Figure 3.11 A pre-hospital team drawing up drugs and preparing

an equipment dump

Figure 3.12 Challenge and response taking place using the checklistprior to PRSI

have working batteries and there should be two blades with

functioning bulbs. An appropriately sized endotracheal tube(ETT) should be prepared: check the cuff does not leak,then fully deflate and lubricate it. An ETT a size smaller 3.3 Preparation 61

than estimated should always be easily accessible in case of

unexpected difficulties. In patients with stridor or suspectedairway oedema, an ETT 1–2 sizes smaller than normal shouldalso be prepared. A suitable bougie (tracheal tube introducer) must beavailable. A 10 mL syringe is required for inflating the ETTcuff, and tape or tie must be prepared for securing the ETTin position once placement is confirmed (or use a specificallydesigned tube holder). Minimum monitoring standards are mandatory (Pulseoximeter, non-invasive blood pressure (NIBP), capnographyand electrocardiogram (ECG)). In certain circumstances fullmonitoring may not be possible. A pulse oximeter may notfunction if the patient is cold or peripherally shutdown andeven grossly assessing the colour of the patient (blue vs. pink)may be difficult in poor lighting. NIBP may need to be donemanually by palpation or simply by ensuring the presenceof a radial pulse. End-Tidal Carbon Dioxide (ETCO2) is thegold standard for confirming tracheal intubation and is alsoimportant for monitoring ventilation during transport, par-ticularly in head injured patients (See Chap. 6). Sedative and paralysing agents should be prepared instandard concentrations and carefully labelled using stan-dardised drug label stickers or permanent ink on the syringebarrel. The doses are then calculated appropriately forthe patient’s weight and condition (Appendix: Drug Dose,Weight & ETT Size Field Guide). Drugs and doses shouldthen be cross-checked with another team member. Preparingessential drugs on a daily basis or using commercial or phar-macy pre-filled syringes may be an option. This reduces therisk of dilution and labelling errors on scene, and also offersthe advantage of a shorter preparation time. Daily-prepareddrugs can be wasteful and expensive if their use is infrequent. Most neuromuscular blocking agents used in pre-hospitalpractice (e.g. Rocuronium, Suxamethonium) ideally requirerefrigerated storage. They degrade over time, and the rate ofdegradation increases with higher temperatures. Where suchdrugs are stored without refrigeration, organisations must62 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

have a system for wasting and replacing drugs that have notbeen used within the designated time period.

3.3.3 Positioning

During PRSI, 360° access to the patient is preferable. In

addition, it is usually easier to perform laryngoscopy with thepatient off the ground. If possible the patient should be on anambulance trolley or elevated spinal board/scoop stretcher inpreparation for induction. Having the trolley at knee heightwith team members kneeling is ideal, as this allows equip-ment and monitors to be left on the ground but within reach. Kneeling to intubate whilst the patient is on a trolley isprobably the best all round position. A trolley is not alwaysimmediately available however, and many pre-hospital intu-bations take place with the patient on the ground. Sitting backfrom the kneeling position onto the plantar flexed feet pro-vides probably the most favoured way of intubating someoneon the ground. To reduce strain on the neck, it is important toposition the knees a few inches back from the patient’s head,giving a better line of sight towards the larynx (Fig. 3.16). An alternative to the ‘kneeling back’ position, is lyingprone (Fig. 3.13a). This brings the intubator’s eyes closer tothe larynx, however it places the intubator at a mechanicaldisadvantage when applying a correct laryngoscopy tech-nique (i.e. pulling ‘up and away’, with the laryngoscope han-dle at 45° to the ground). The prone position places emphasison the anterior deltoid muscle and causes a tendency to leverback on the top teeth to improve the view, particularly in amore difficult intubation. The seated position with legs either side of the patient’schest is another alternative (Fig. 3.13b). This provides a stableposition with good mechanical advantage; it allows the stron-ger bicep muscle to be used and the elbow of the left arm canbe supported against the left thigh if needed. It also requiresless space at the head of the patient, however it can interferewith positioning of the equipment dump and moves the per-son providing MILS slightly further away from the patient. 3.3 Preparation 63

Figure 3.13 Alternative intubating positions (a) Lying prone, (b)

Sitting

The trained assistant is ideally positioned facing the intu-

bator on the side of the patient where IV access has beengained (it is slightly easier if this is on the patient’s right so the64 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

Figure 3.14 One assistant applies cricoid pressure and passes

equipment whilst one assistant provides MILS

assistant can easily pass airway items into the right hand ofthe intubator). The kit dump is placed between the intubatorand assistant so that both are able to reach kit if required. Ifon the right side of the patient, the assistant provides cricoidpressure with the right hand and passes equipment with theleft and vice versa (Fig. 3.14). Given the potential for inap-propriately applied cricoid pressure to be either ineffectiveor to impede intubation, it is not advisable to ask others withlittle or no experience of the technique to take on this role. If IV access is in the arm, either the intubator or the assis-tant should then be able to reach the cannula and administerdrugs. It may be preferable (or necessary if only tibial IOaccess is available) for an additional person to administerdrugs. Instructions regarding drug doses must be explicit andunderstood prior to commencing PRSI. This extra person canalso be used to continuously palpate the radial pulse duringinduction, in order to promptly detect the requirement for avasopressor/inotrope/fluid. Without this additional person, itis easy for the intubator and assistant to become focused onthe airway and fail to notice, and respond promptly to a dropin blood pressure. 3.3 Preparation 65

The monitor is placed so that both the intubator and assis-

tant can see it. This usually means next to the kit dump, butfurther away from the patient. If the patient is on a trolley,this may require the monitor to be tilted back to get a clearview of the screen. The “sniffing the morning air” position (Fig. 3.15); withthe neck flexed and head extended, is the ideal intubatingposition, however this is not appropriate if there is a pos-sibility of cervical spine injury. If manual in-line stabilisation(MILS) of the cervical spine is required, it is carried out fromthe opposite side to the trained assistant. If any task is to bedevolved to a non-team member, it is MILS, as it is relativelyeasy to instruct another member of the emergency services toundertake this role. It may be useful to position a bystander at the foot of thecasualty in order to tilt the patient head down should theoropharynx fill with vomit or blood during induction. A func-tioning high pressure, high volume suction unit should alwaysbe immediately to hand with a manual unit in reserve.66 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

3.3.4 Protection

3.3.4.1 Cervical Spine Injury

A cervical spine injury will have been sustained by 2.4 %

of blunt trauma victims (Crosby 2006). If the GCS is <8 thisfigure increases to 10.2 %. The indications for PHA (e.g.respiratory compromise, reduced GCS etc.), will precludepre-hospital clearance of the cervical spine as the patient willeither not be fully conscious or will have a distracting injury.Therefore, if the mechanism of injury is consistent with a cer-vical spine injury, MILS should be initiated.

Manual In-Line Stabilisation (MILS)

When three or more team members are present, MILS is bestperformed from the opposite site of the casualty to the assis-tant, approaching over the front of the chest (Fig. 3.16). MILScan alternatively be applied from above the patient’s head,on either side of the intubator, but this involves sharing a lim-

Figure 3.16 MILS can be performed over the chest from the oppo-site side to the assistant 3.3 Preparation 67

Figure 3.17 Correct MILS hand position with thumbs applying

pressure down on mastoid processes behind the ears leaving the jawfree to move during laryngoscopy

ited space and can impede the intubation process. The aim ofMILS is to oppose the forces generated by laryngoscopy andis achieved by firmly holding down the patient’s mastoid pro-cesses (Fig. 3.17). This affords a good mechanical advantage tooppose movement during laryngoscopy and reduces the degreeof head extension by 50 % (Hasting and Wood 1994). Whenonly two team members are in attendance a “careful” intuba-tion may be all that is possible. Intubating whilst attempting tostabilise the head between the knees in a kneeling position ispossible, but this requires an awkward leaning back position toview the larynx, which is a strain in a difficult intubation. If the patient is already immobilised with a hard collarand head blocks, these should be removed (the collar may68 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

simply be opened or the front part removed) and replaced by

MILS. Full spinal immobilisation is independently associatedwith an increased risk of difficult intubation (Heath 1994).Removing the collar significantly improves mouth opening(Goutcher and Lochead 2005), but MILS will still impedea view at laryngoscopy compared to the optimum position.Nolan reported a reduced view in 45 % of “normal” electivepatients, with no view of the larynx at all in 22 % (Nolanand Wilson 1993). Reassuringly, although five patients wereunable to be intubated directly, all were intubated success-fully with the use of a bougie. A bougie is superior to a mal-leable stylet to aid intubation (Gataure et al. 1996; Noguchiet al. 2003), and should be used routinely in PRSI to increaseintubation success. Performing a RSI with MILS using agum elastic bougie is very unlikely to cause further cervicalspine movement (Crosby 2006). However, always remember:Failure to oxygenate may kill the patient; moving the neckwill probably not.

3.3.4.2 Cricoid Pressure

This is a technique used in anaesthesia to decrease the riskof aspiration during induction. The application of cricoidpressure is also known as Sellick’s manoeuvre after theanaesthetist who first described it in 1961 (Sellick 1961).During induction the tone of the upper oesophageal sphinc-ter is reduced and the airway reflexes lost. This means thatgastric contents may passively move up the oesophagus, intothe oropharynx and soil the airway. The application of cricoidpressure compensates for this loss of tone by compressing theproximal oesophageal lumen between the cricoid cartilageand the cervical vertebrae. The cricoid cartilage is chosen, as it is the only part ofthe airway that consists of a complete ring of cartilage(Fig. 3.18). The thyroid cartilage and tracheal rings have onlysoft tissue posteriorly and are ineffective at compressing theoesophagus. Cricoid pressure is a 3-finger technique. Sellick describedthe manoeuvre as follows: “Before induction the cricoid is 3.3 Preparation 69

Hyoid bone

Thyroid cartilage

Median cricothyroid ligament

Cricoid cartilage Trachea

Figure 3.18 Upper airway anatomy

palpated and lightly held between the thumb and second fin-ger; as anaesthesia begins, pressure is exerted on the cricoidcartilage mainly by the index finger.” Sellick reported the technique as a 1-handed manoeuvre.Some groups have advocated the use of a 2-handed technique,with the second hand providing counter pressure behind theneck. This technique may have utility as when anterior forceis applied, neck flexion is possible. This may potentiallyexacerbate a cervical spine injury. It appears, however, thatwhen the correct force is used in the correct direction, thereis no clear additional advantage to the provision of posteriorneck support (Cook 1996; Vanner et al. 1997). Therefore, inboth the hospital and pre-hospital environment a 1-handedtechnique is usual. This technique has the added advantageof allowing the assistant to deliver cricoid pressure and passequipment during intubation.70 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

It has been shown that a force of 30 N is necessary to

achieve oesophageal occlusion and prevent regurgitation(Vanner and Asai 1999). This pressure is described as “firmpressure” or that required to cause pain when applied to thebridge of the nose. Smith and Dejoy (2001) recommended applying 10 N offorce prior to induction and then 30 N when the patient losesconsciousness. More than 20 N of force is uncomfortable andcan cause retching, so it is preferable to simply position thefingers over the cricoid cartilage prior to induction ratherthan accidentally applying excessive pressure too early. Correctly applied cricoid pressure may enhance the laryn-goscopic view and facilitate intubation in some patients. Morelikely, it will impede the view at laryngoscopy (Haslam et al.2005). Excessive force (>40 N) may lead to distortion of theupper airway. This may make both intubation more difficult,and impede mask ventilation in the event of a failed intuba-tion. Cricoid pressure should be applied directly backwards,but it is easy to accidentally apply pressure to either theleft or right (usually the opposite side to the person apply-ing the pressure). The intubator should be aware of thesepotential problems and be prepared to move the hand of theassistant in an attempt to visualise the larynx. The intubatorshould have a low threshold for requesting reduction or evenremoval of cricoid pressure if they consider that their view isbeing impeded by its application. In addition to the above problems, inadequate pressuremay be ineffective and still allow regurgitation. Similarly,pressure applied in the wrong place, (e.g. thyroid cartilage)will not be effective either. Given the potential for problems,it is important that the assistant is trained and proficient inthis technique, particularly when the intubator is relativelyinexperienced. It is well recognised that even experiencedanaesthetic assistants may have a poor technique if notrecently practised. However, this can be easily improved bya very short period of simple retraining (May and Trethewy2007; Owen et al. 2002). Experience in delivering the correctpressure can be achieved using mechanical simulators, kitchen 3.3 Preparation 71

scales or even a 50 mL syringe (compressing the plunger on a

capped off, air-filled 50 mL syringe to 33 mL approximates to30 N) (Flucker et al. 2000; Herman et al. 1996). If passive regurgitation occurs, pressure should be increasedand the oropharynx suctioned immediately. Conversely, cri-coid pressure should actually be released if active vomitingoccurs at induction. This may occur before any/sufficientinduction agent has been given, and can sometimes be pro-voked by excessive and early cricoid pressure. In this casethe continued application of force to the cricoid can result inoesophageal rupture. Cricoid pressure should be applied as the patient losesconsciousness or ceases respiratory effort (if already uncon-scious). Ideally it should not be released before the endo-tracheal tube has been placed, the cuff inflated, and itsposition confirmed. The caveat to this is that removal may berequested to improve the view at laryngoscopy, as describedabove. It is permissible to gently ventilate the lungs withcricoid pressure in situ, should it be necessary to maintainadequate oxygenation prior to laryngoscopy, as this shouldreduce gas entering and distending the stomach. In a prospective observational study of 402 patients, Harriset al. (2010) reported on the effects of cricoid pressure andlaryngeal manipulation in a UK HEMS service. They comparedthe effect on laryngoscopic view of three laryngeal manoeu-vres; release of cricoid pressure, BURP or laryngeal manipu-lation. These manoeuvres were used during 61 intubationswhen the intubator was either unable to see the cords or topass the bougie through the cords. The laryngoscopic view wasimproved by at least one Cormack-Lehane grade with releaseof cricoid pressure in 11 of 22 patients (50 %), with laryngealmanipulation in 15 of 25 patients (60 %), and with BURP in9 of 14 patients (64 %). No manoeuvre made the view worse.Release of cricoid pressure was followed by regurgitation intwo patients, both of whom had received prolonged BVMventilation. Given the evidence of pre-hospital aspiration describedearlier, the benefit of cricoid pressure is not proven. It is most72 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

likely to be beneficial in those who have not yet lost laryn-

geal reflexes (i.e., GCS >8), in order to reduce aspiration riskwhen they relax under anaesthesia. To avoid confusion, it isadvisable to use cricoid pressure for every PRSI, but to beaware of the limited evidence and have a low threshold foradjusting/releasing it when faced with a difficult intubation.

3.4 PremedicationPretreatment with a drug (before giving the induction agent)is usually aimed at obtunding the sympathetic response tolaryngoscopy whilst allowing a reduced dose of inductionagent to be used to achieve the same end result. The pretreat-ment drugs are therefore ideally more cardiostable than theinduction agents. Examples of drugs used for pretreatmentinclude Fentanyl and Alfentanil.

3.5 Paralyse and Sedate

The induction phase should only be commenced when allpreparation is complete. Other than in peri-arrest situations,the team should have already run through the PRSI checklistto ensure that nothing has been missed. PRSI should then begin with the administration of aninduction agent, (preceded by pretreatment if appropriate).The dose of the induction drug should be adjusted to accountfor level of consciousness, other drugs already given/taken,volume status, blood pressure and ICP. Many inductionagents cause hypotension. This hypotension may result fromperipheral vasodilatation, a reduction in cardiac contractilityor a reduction in intrinsic sympathetic tone. Hypotensionis most marked in hypovolaemic patients but may not beimmediately obvious after intubation due to the sympatheticresponse to laryngoscopy. Ketamine is an exception to thisrule, and blood pressure is usually maintained due to itsaction on the sympathetic nervous system. 3.5 Paralyse and Sedate 73

Hypotension is a predictable side effect, and vigilance with

prompt management is essential. Ideally one person shouldbe tasked to monitor the radial pulse both during and afterinduction. Prophylactic treatment may be considered in cer-tain situations, with a fluid bolus being administered prior toinduction. A vasopressor or inotrope should be on hand tomanage episodes of hypotension resistant to fluid therapy. Loss of consciousness (e.g. loss of eyelash reflex or loss ofverbal response) is normally assured prior to administrationof the muscle relaxant (paralysing agent). Suxamethonium1.5 mg/kg was traditionally used because of its rapid onset,but is associated with many side effects (Box 3.7). It is fre-quently cited that a benefit of Suxamethonium over othermuscle relaxants is its short duration of action. The sugges-tion was that in the event of failed intubation the patientwould recommence spontaneous respiration and thereforeavoid critical hypoxia. In reality, critical desaturation is likelyto occur prior to muscular activity returning, so assisted ven-tilation will be required (Benumof et al. 1997). As it is easierto ventilate a fully relaxed patient in the event of failed intu-bation, this argument does not hold. More significantly, thevast majority of patients undergoing PRSI are not suitableto be safely managed ‘awake’. Continued anaesthesia andparalysis with an alternative form of advanced airway wouldbe preferable. Rocuronium 1.2 mg/kg has a slightly increasedonset time compared to Suxamethonium, but many fewerside effects (although there is still an incidence of anaphy-laxis) (see Chap. 6). For these reasons, Rocuronium is nowwidely used in PHA throughout the UK. The paralysing agent should always be followed by a flushto ensure the drug reaches its point of action in as short atime as possible. The onset of paralysis may be prolongedin a patient with a low cardiac output state. When usingSuxamethonium its onset is usually heralded by fascicula-tions but these are not always seen. Non-depolarising musclerelaxants, such as Rocuronium, do not generate fasciculations.As a guide, laryngoscopy should be attempted only when themouth opens freely. This equates well to cord paralysis.74 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

Box 3.7: Side Effects of Suxamethonium

3.6 Passage of Tube

The aim is to be swift but not rushed. The whole processshould take no more than 1 min. The vocal cords are attached anteriorly to the thyroid car-tilage and posteriorly to the arytenoid cartilages (Figs. 3.18and 3.19). The view is described by the Cormack and Lehaneclassification (Fig. 3.20). A modification divides grade 2 into:

Laryngoscope Tongue

Epiglottis Vocal cords

Trachea Bougie

Arytenoids Oesophagus

Figure 3.19 View at laryngoscopy (manikin)

3.6 Passage of Tube 75

Grade I Grade II Grade III Grade IV

Figure 3.20 Cormack and Lehane intubation grade (Reproduced

with kind permission Anaesthesia UK Website)

grade 2a: part of the vocal cords are seen and 2b: only thearytenoids seen. This should be recorded along with addi-tional equipment required (e.g., McCoy blade) and handedover to other medical personnel, indicating the difficulty orotherwise of intubation. A poor view may be improved by Backward Upward(pushing an anterior larynx backwards and then up towardsthe laryngoscope) Rightward (as the laryngoscope is comingin from the right side of the mouth/tongue) Pressure (BURP)on the thyroid and cricoid cartilages together.

3.6.1 Laryngoscope

A Macintosh size 3 laryngoscope is suitable for most adults

and is easier to insert than a size 4 when mouth opening islimited. A size 4 may be required in patients with a large jaw.Care should be taken not to insert a size 4 too far initially asit is easy to pass the larynx and reach the oesophagus whichcan be difficult to recognise for the inexperienced. A McCoy blade, which has a flexible tip, (Fig. 6.6) hasbeen shown to significantly improve the view at laryngoscopywhen the neck is immobilised (Gabbott 1996). There is there-fore an argument for using one routinely in the pre-hospitalenvironment. Unfortunately they are not currently availablein disposable form and require appropriate cleaning betweenpatients. Many practitioners are also not experienced in thetechnique required to use a McCoy laryngoscope. Other laryngoscope devices including indirect laryngo-scopes (e.g. Airtraq®) (Fig. 6.7) and video laryngoscopes (e.g.Glidescope®) (Fig. 6.8), have been demonstrated to improve76 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

laryngoscopic view and intubation success rate in patients

with cervical spine immobilisation or other predicted ‘dif-ficult’ airways in the hospital setting (Maharaj et al. 2007;Malik et al. 2009; McElwain and Laffey 2011). These havegreat potential to be useful airway devices in the pre-hospital setting, but as yet evidence for their use is limited.Contamination (such as blood and vomit) in the airways ofpre-hospital patients, poses a significant challenge to the opti-cal arrangements of such laryngoscopes (Trimmel et al. 2011),and personnel should have experience and regular trainingwith these devices before attempting to use them for PRSI.

3.6.2 Bougie

A gum elastic bougie (or disposable tracheal introducer of

a similar design) should be used electively in all PRSIs dueto the increased incidence of difficult intubation (Figs. 3.21and 3.22). When only the arytenoids are visible, by using abougie, correct placement should still be relatively straight-forward. Even when only the epiglottis is seen, this can beused as a landmark to guide the blind placement of a bougie.

a b

Figure 3.21 (a) A view of the bougie passing between the cordswith tip angled anteriorly. (b) The intubator passing a bougiethrough the vocal cords before an ETT is railroaded over the top 3.6 Passage of Tube 77

The “click” of the tip of the bougie passing over the tra-cheal cartilages may be felt, confirming correct placement.Alternatively, resistance will occur as the bougie reaches thecarina or bronchi, whereas it will generally pass unhindereddown the length of the oesophagus. The latter technique canonly be used if the bougie is used independently then theETT railroaded over afterwards by the assistant (rather thanpreloading the ETT on the bougie). Preloading the ETT alsorequires the bougie to be held firmly below the tip of theETT to allow control of the tip. This is best understood bypractise on a manikin. A bougie needs to be either stored straight or gentlycurved with the angled tip on the inside of the curve. A bentor misshapen bougie can be very difficult to use. In hot tem-peratures, a gum elastic bougie can become very soft andunusable; storing in a cool box may be necessary to maintainsome rigidity. A bougie made of an alternative material maytherefore be preferable in a hot environment. The ETT will sometimes be held up as the tip catches onthe vocal cords. This can be resolved by rotating the ETTanticlockwise 90° in the majority of cases. Occasionally cri-coid pressure will need to be released.

a b

Figure 3.22 (a) An ETT being passed over a bougie with the laryn-goscope in the vallecula, (b) The bougie is held still by the assistantwhile the intubator railroads the ETT through the vocal cords78 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

The incidence of complications markedly increases after

two failed attempts at passing an endotracheal tube (Mort2004). For this reason, after two attempts the failed intuba-tion drill is followed. It is only worth attempting intubationfor a second time if something is going to be changed forthe second attempt i.e. position of the patient, different sizeblade, different laryngoscope type (e.g. McCoy, Airtraq™).Repeating exactly the same manoeuvre will likely give thesame view and delay the establishment of adequate oxygen-ation/ventilation by another means. Ventilation should becarried out between attempts if required to maintain SpO2above 92 %.

3.6.3 Plan A and Plan B

When embarking on an RSI it is essential to be clear not

only about your primary objective but also to have a pre-pared fallback position should things go wrong (Box 3.8).As previously mentioned, in the pre-hospital environment,when faced with a failed intubation, waking the patient up isunlikely to be clinically appropriate.

Box 3.8: Planning for PRSI

3.6.4 Failed Intubation Drill (Appendix “Failed

Intubation Protocol”)In the event of a failure to intubate during PRSI a well-rehearsed drill should increase the likelihood of a good out-come. The intubator should rapidly recognise that the situationrequires the implementation of the “Failed Intubation Drill”and should clearly declare this to the assistant. The assistantshould then immediately release cricoid pressure and pass 3.7 Post Intubation 79

the LMA (Appendix “Use of the Laryngeal Mask Airway”)

or other supraglottic airway device (SAD). If a LMA isused there are advantages to using one that allows higherventilation pressures to be delivered e.g. ProsealTM LMA(Fig. A.3). The assistant should then immediately prepare thesurgical cricothyroidotomy kit in case this is required. If ven-tilation is unsuccessful with the rescue device, ventilation witha BVM and oropharyngeal airway should be attempted, whilstthe most experienced team member performs a surgical crico-thyroidotomy (Appendix “Emergency Cricothyroidotomy”).When Suxamethonium is the muscle relaxant used, it may bebeginning to wear off. A second dose should be avoided, as itcan induce a profound bradycardia; a non-depolarising musclerelaxant, such as Rocuronium, should be used instead.

3.7 Post Intubation

3.7.1 Confirmation of Placement

Unrecognised oesophageal intubation is a preventable and

catastrophic complication of PRSI. The gold standard forensuring correct ETT positioning is the presence of ETCO2using capnography (See Chap. 6). Other methods are used to confirm correct placement, butcan be misleading and are not infallible. These include: Visual Confirmation: The ETT may be seen to pass through the cords. Unfortunately the view is often not ideal, and when railroading the tube, any view one had of the larynx, may be blocked by the passing tube. Auscultation: Listening (in both axillae) with a stethoscope may confirm air entry in the lungs. It will also confirm bilateral ventilation and confirm that the tube has not been inserted too far i.e., into the right main bronchus. Unfortunately breath sounds can be difficult to hear in some patients (e.g., obese, emphysema) and this is often exacerbated in the pre-hospital environment due to external noise.80 Chapter 3. Pre-hospital Rapid Sequence Intubation (PRSI)

Look and Feel: Chest movement may be seen or felt with

hands placed on the chest. This is not very reliable. Oesophageal Detector: These are commercial devices based on the “Wee oesophageal detector.” They are essentially large syringes that are attached to the ETT, and an attempt is made to rapidly withdraw air. If the tube is in the trachea, this is easy to do, if in the oesoph- agus, resistance is felt due to collapse of the compliant walls of the oesophagus. This technique can be reassur- ing in patients in cardiac arrest when minimal carbon dioxide is being produced and this cannot be detected convincingly by any of the methods described earlier. An oesophageal detector is accurate in adult patients, however false positives can occur in very obese patients and children due to collapse of the trachea.